Pore size influences nature of complex nanostructures

January 14, 2019

ITHACA, N.Y. - Building at the nanoscale is not like building a house. Scientists often start with two-dimensional molecular layers and combine them to form complex three-dimensional architectures. And instead of nails and screws, these structures are joined together by the attractive van der Waals forces that exist between objects at the nanoscale.

Van der Waals forces are critical in constructing materials for energy storage, biochemical sensors and electronics, although they are weak when compared to chemical bonds. They also play a crucial role in drug delivery systems, determining which drugs bind to the active sites in proteins.

In new research that could help inform development of new materials, Cornell chemists have found that the empty space ("pores") present in two-dimensional molecular building blocks fundamentally changes the strength of these van der Waals forces, and can potentially alter the assembly of sophisticated nanostructures.

The findings represent an unexplored avenue toward governing the self-assembly of complex nanostructures from porous two-dimensional building blocks. "We hope that a more complete understanding of these forces will aid in the discovery and development of novel materials with diverse functionalities, targeted properties, and potentially novel applications," said Robert A. DiStasio Jr., assistant professor of chemistry in the College of Arts and Sciences.

In a paper titled "Influence of Pore Size on the van der Waals Interaction in Two-Dimensional Molecules and Materials," published Jan. 14 in Physical Review Letters, DiStasio, graduate student Yan Yang and postdoctoral associate Ka Un Lao describe a series of mathematical models that address the question of how void space fundamentally affects the attractive physical forces which occur over nanoscale distances.

In three prototypical model systems, the researchers found that particular pore sizes lead to unexpected behavior in the physical laws that govern van der Waals forces. Further, they write, this behavior "can be tuned by varying the relative size and shape of these void spaces ... [providing] new insight into the self-assembly and design of complex nanostructures."

While strong covalent bonds are responsible for the formation of two-dimensional molecular layers, van der Waals interactions provide the main attractive force between the layers. As such, van der Waals forces are largely responsible for the self-assembly of the complex three-dimensional nanostructures that make up many of the advanced materials in use today.

The researchers demonstrated their findings with numerous two-dimensional systems, including covalent organic frameworks, which are endowed with adjustable and potentially very large pores.

"I am surprised that the complicated relationship between void space and van der Waals forces could be rationalized through such simple models," said Yang. "In the same breath, I am really excited about our findings, as even small changes in the van der Waals forces can markedly impact the properties of molecules and materials."
The work received funding from the Cornell Center for Materials Research and the National Science Foundation, and computational resources from the National Energy Research Scientific Computing Center through the U.S. Department of Energy.

Cornell University

Related Nanostructures Articles from Brightsurf:

Unlocking PNA's superpowers for self-assembling nanostructures
Researchers at Carnegie Mellon University have developed a method for self-assembling nanostructures with gamma-modified peptide nucleic acid, a synthetic mimic of DNA.

Machine learning enhances light-matter interactions in dielectric nanostructures
The discovery has promising possibilities for the development of a wide range of photonic devices and applications including those involved in optical sensing, optoacoustic vibrations, and narrowband filtering.

Electron correlations in carbon nanostructures
Graphene nanoribbons are only a few carbon atoms wide and have different electrical properties depending on their shape and width.

Paving a way to achieve unexplored semiconductor nanostructures
A research team of Ehime University paved a way to achieve unexplored III-V semiconductor nanostructures.

Nanostructures help to reduce the adhesion of bacteria
Scientists has shown how bacteria adhere to rough surfaces at the microscopic level.

Diamonds are forever: New foundation for nanostructures
Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have fabricated a novel glass and synthetic diamond foundation that can be used to create miniscule micro -- and nanostructures.

How do atoms vibrate in graphene nanostructures?
Researchers from the University of Vienna, the Advanced Institute of Science and Technology in Japan, the company JEOL and La Sapienza University in Rome have developed a method capable to measure all phonons existing in a nanostructured material.

Heterophase nanostructures contributing to efficient catalysis
In the research on phase engineering of noble metal nanomaterials, amorphous/crystalline heterophase nanostructures have exhibited some intriguing properties.

Dresden physicists use nanostructures to free photons for highly efficient white OLEDs
Thanks to intensive research in the past three decades, organic light-emitting diodes (OLEDs) have been steadily conquering the electronics market -- from OLED mobile phone displays to roll-out television screens, the list of applications is long.

Self-healing DNA nanostructures
DNA assembled into nanostructures such as tubes and origami-inspired shapes could someday find applications ranging from DNA computers to nanomedicine.

Read More: Nanostructures News and Nanostructures Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.